Serine $(HOCH_2CH(NH_2)COOH)$ is an amino acid. The correct Fischer projection of $L$-serine is:

Which of the following amino acids is chiral?

In $\text{alanyl-glycyl-leucyl-alanyl-valine}$,the number of peptide linkages is $......$

In the following compound,the favourable site/s for protonation is/are:
(Image description: Adenine structure with labels $a$ on the exocyclic $-NH_2$ group,$b$ on the pyrimidine ring nitrogen,$c$ on the other pyrimidine ring nitrogen,$d$ on the imidazole ring nitrogen,and $e$ on the imidazole ring $-NH-$ group.)

During the denaturation of proteins,which of these structures will remain intact?

Proteins when heated with conc. $HNO_3$ give a yellow colour. This is